The most promising methods of providing real-time weld process sensors for weld tracking have utilized some variation of optical sensing. The emerging vision technologies have included a coaxial optical system which involves the placement of the primary imaging lens within the surrounding housing of the electrode such that the lens optical axis is aligned with the electrode. The field of view is limited to the exit diameter of the housing or gas cup surrounding the electrode. Usually a fiberoptic image bundle is utilized to optically transmit the image to a camera in a remote location. Thus, the camera electronics are in a location remote from the harsh welding environment.
The lack of uniformity of light in the welding area--the welding arc being too bright and surrounding welding area too dark--has proven to be detrimental in using through-the-torch viewing because of the difficulty in recognizing features in the image which have widely different brightness. One solution to this problem was having large, expensive, bright, quartz, halogen electric lights directed onto the weld area, but this solution has not worked well.